1. Field of the Disclosure
This disclosure relates to a light emitting diode, and more particularly to a light emitting diode adapted to improve light efficiency and a backlight unit and a liquid crystal display (LCD) device including the same.
2. Description of the Related Art
Cathode ray tubes (CRTs) correspond to one of display devices which are widely used. The CRTs are mainly used as monitors for TVs, measuring apparatuses, information terminals, and so on. However, the heavy weight and large size of the CRTs have been a major hindrance to the manufacturing of small, light electronic products.
To address this matter, LCD devices are gradually being used in a wide range of applications due to their advantages such as light weight, thin thickness, low power consumption, and others. Furthermore, the LCD devices are being manufactured to have even larger screens, be thinner, and consume less power, in order to meet requirements of users.
Such LCD devices display images by controlling the amount of light transmitted through liquid crystal. However, the LCD devices are not self-illuminating display devices, unlike CRTs. As such, the LCD devices each include a backlight unit configured to have a separate light source, which provides light necessary to display an image, and disposed on the rear surface of an LCD panel. The backlight unit is classified as either an edge type or a direct type in accordance with the disposition of its light source.
The edge type backlight unit includes a light source which is disposed in a position corresponding to a side of the LCD panel. Also, the edge type backlight unit irradiates light emitted from the light source onto the entire surface of the LCD panel using a light guide plate.
On the other hand, the direct type backlight unit includes a plurality of light sources arranged at a fixed distance under the LCD panel. The plurality of light sources directly applies light to the rear surface of the LCD panel. Such a direct type backlight unit can provide a higher brightness and a wider luminescent surface than the edge type backlight unit because it employs plurality of light sources.
The backlight unit includes any one of a lamp and a light emitting diode, as a light source. Recently, the light emitting diode is mainly used in the backlight unit because it easily allows the backlight unit to be thinner and to consume less power. More particularly, a white light emitting diode is used as a light source of the backlight unit. The white light emitting diode makes blue color light generated in a blue color light emitting chip to be transmitted through a fluorescent material and converted into white color light.
The light emitting diode has a long life span and strong directivity of light emission. The light emitting diode can be small-sized, light-weight, driven with a low voltage, and packaged in a variety of shapes. The light emitting diode well endures impact and vibration. Also it does not require a preheating time or a complicated driving circuit. As such, the light emitting diode is expected to be replaced with an incandescent electric lamp, a fluorescent lamp, a mercury lamp, and others within the next few years. Moreover, since the light emitting diode has a large energy band gap, it can output a wide wavelength bandwidth range of light including red light to ultraviolet-ray light. Furthermore, as the light emitting diode has superior physical and chemical stability, it attracts public attention in that it may realize high efficiency and a high output.
However, the light emitting diodes developed up to the present can not satisfy the aspects of light output, light emitting efficiency and cost. As such, the light emitting diode must be improved to have better performance. Particularly, the light efficiency of the light emitting diode is lowered in the process of converting blue light generated from the light emitting chip into white color light by transmitting blue color light through the fluorescent material.